Impact of Land Use/Cover Change on Ecosystem Service Values in the Kilombero Valley Floodplain, Southeastern Tanzania

Land use/cover change (LUCC) attributed to natural factors and human activities has led to the loss of ecosystem services, making the quantitative valuation of ecosystem services the scientific focal pointfor sustainable development. This study assessed changes in the ecosystem services values (ESVs) due to LUCC during the period 1990–2016 in the Kilombero Valley floodplain, located in southeastern Tanzania. Moderate resolution Landsat images from 1990, 2010 and 2016 were obtained and analyzed using a random forest (RF) algorithm for classification, and ArcGIS Desktop software (version 10.2, Esri, Redlands, CA, USA) for mapping to assess the LUCC. The ESVs were estimated based on the benefit transfer approach using adopted global value coefficients and modified local value coefficients. The results revealed that the aggregated ESVs of the forests, bushlands, wetlands, and water had decreased, consequently leading to a total loss of US$ 811.5 million (26.6%) in ESVs over the past 26 years when calculated with the modified local value coefficients to US$ 3000.7 million (42.3%) when calculated with global value coefficients. Moreover, the loss in the ESV was attributed to the decreased values of water regulation, climate regulation, erosion control, nutrient cyclying, habitat/refugia, and water supply, with the exception of the values of food production and biological control, which gradually increased during the study period. This study provided minimum estimates of the ecosystem service values, which willcontribute to the formulation of policy actions and strategies for sustainable management of the Kilombero Valley floodplain and inform various stakeholders on the tradeoffs involved in the use of land resources.

Ultra-Low Volume Application of Spinosad (Natular 2EC) as a Residual in a Hot-Arid Environment Against Aedes aegypti

ABSTRACT The invasive Aedes aegypti is an important disease vector increasing in frequency in hot-arid regions of the USA such as the Southwest. Within hot-arid surroundings this mosquito may be confined to peridomestic locations that tend to be cooler and humid, such as in lush, irrigated ornamental vegetation surrounding homes. However, to reach these habitat refugia, ultra-low volume (ULV) applications of insecticides targeting this mosquito must retain efficacy after being sprayed from the air or street where hot-arid conditions are prevalent. We investigated the efficacy of a biologically based larvicide, spinosad (Natular 2EC), applied as a ULV in a hot-arid environment targeting Aedes aegypti. We found that this pesticide is able to penetrate this environment and has the potential to act as a residual.

Macroinvertebrate community responses to a dewatering disturbance gradient in a restored stream

Dewatering disturbances are common in aquatic systems and represent a relatively untapped field of disturbance ecology, yet studying dewatering events along gradients in non-dichotomous (i.e. wet/dry) terms is often difficult. Because many stream restorations can essentially be perceived as planned hydrologic manipulations, such systems can make ideal test-cases for understanding processes of hydrological disturbance. In this study we used an experimental drawdown in a 440 ha stream/wetland restoration site to assess aquatic macroinvertebrate community responses to dewatering and subsequent rewetting. The geomorphic nature of the site and the design of the restoration allowed dewatering to occur predictably along a gradient and decoupled the hydrologic response from any geomorphic (i.e. habitat heterogeneity) effects. In the absence of such heterogeneous habitat refugia, reach-scale wetted perimeter and depth conditions exerted a strong control on community structure. The community exhibited an incremental response to dewatering severity over the course of this disturbance, which was made manifest not as a change in community means but as an increase in community variability, or dispersion, at each site. The dewatering also affected inter-species abundance and distributional patterns, as dewatering and rewetting promoted alternate species groups with divergent habitat tolerances. Finally, our results indicate that rapid rewetting – analogous to a hurricane breaking a summer drought – may represent a recovery process rather than an additional disturbance and that such processes, even in newly restored systems, may be rapid.

Macroinvertebrate community responses to a dewatering disturbance gradient in a restored stream

Dewatering disturbances are common in aquatic systems and represent a relatively untapped field of disturbance ecology, yet studying dewatering events along gradients in non-dichotomous (i.e., wet/dry) terms is often difficult. Because many stream restorations can essentially be perceived as planned hydrologic manipulations, such systems can make ideal test-cases for understanding processes of hydrological disturbance. In this study we used an experimental drawdown in a 440 ha stream/wetland restoration site to assess aquatic macroinvertebrate community responses to dewatering and subsequent rewetting. The geomorphic nature of the site and the design of the restoration allowed dewatering to occur predictably along a gradient and decoupled the hydrologic response from any geomorphic (i.e., habitat heterogeneity) effects. In the absence of such heterogeneous habitat refugia, reach-scale wetted perimeter and depth conditions exerted a strong control on community structure. The community exhibited an incremental response to dewatering severity over the course of this disturbance, which was made manifest not as a change in community means but as an increase in community variability, or dispersion, at each site. The dewatering also affected inter-species abundance and distributional patterns, as dewatering and rewetting promoted alternate species groups with divergent habitat tolerances. Finally, our results indicate that rapid rewetting – analogous to a hurricane breaking a summer drought – may represent a recovery process rather than an additional disturbance and that such processes, even in newly restored systems, may be rapid.

The Effects of Fishing on Coral Reef Fish Abundance and Diversity

The effect of artisanal fishing on the abundance and diversity of coral reef fish assemblages was investigated in the Kisite Marine National Park and Mpunguti Marine National Reserve at Shimoni, Kenya. Fishing is prohibited within the Park whereas in the Reserve artisanal fishing using traditional methods is practised. Visual censuses of six representative reef fish families (Chaetodontidae, Lethrinidae, Lutjanidae and Serranidae in 1992 and 1994, and Labridae and Pomacentridae in 1994 only) were undertaken along 250×10 m band transects on two similar pairs of reefs subject to differing fishing pressure. The abundance of commercial species (Lethrinidae, Lutjanidae and Serranidae) was depressed in the Reserve. The unfished butterflyfishes (Chaetodontidae) and damselfishes (Pomacentridae) also showed a greater abundance in the Park than in the Reserve. However, neither species number nor Shannon diversity (H′) of any of these families was affected by fishing pressure. Possible reasons for these findings are discussed. The abundance of commercial species, though not of non-commercial unfished species, increased significantly in the Reserve between 1992 and 1994, suggesting that the unfished Park may be acting as a source of larvae or supply of emigrating adults for the depleted Reserve. The results are comparable with other recent studies describing the effects of fishing pressure and also with those studies detailing the effects of habitat refugia in coral reef areas.